org.springframework.expression.spel
Class ExpressionState

An ExpressionState is for maintaining per-expression-evaluation state, any changes to it are not seen by other
expressions but it gives a place to hold local variables and for component expressions in a compound expression to
communicate state. This is in contrast to the EvaluationContext, which is shared amongst expression evaluations, and
any changes to it will be seen by other expressions or any code that chooses to ask questions of the context.

It also acts as a place for to define common utility routines that the various Ast nodes might need.